CXCL11 (ITAC) is one of three chemokines known to bind the receptor CXCR3, the two others being CXCL9 (Mig) and CXCL10 (IP-10). CXCL11 differs from the other CXCR3 ligands in both the strength and the particularities of its receptor interactions: It has a higher affinity, is a stronger agonist, and behaves differently when critical N-terminal residues are deleted CXCL11 takes on the canonical chemokine fold but exhibits greater conformational flexibility than has been observed for related chemokines under the same sample conditions. Unlike related chemokines such as IP-10 and IL-8, ITAC does not appear to form dimers at millimolar concentrations. The origin for this behavior can be found in the solution structure, which indicates a beta-bulge in beta-strand 1 that distorts the dimerization interface used by other CXC chemokines.

The sequence of the first five N-terminal amino acids was determined and was found to be, Phe-Pro-Met-Phe-Lys.

Dimers and Aggregates

Less than 1% as determined by silver-stained SDS-PAGE gel analysis.

Biological Activity

Recombinant Human I-TAC is fully biologically active when compared to standard. The Activity is calculated by the ability to chemoattract IL-2 activated T-cells using a concentration of 0.1-10 ng/ml.

Endotoxin

0.1ng/ug (IEU/ug) of Human I-TAC.

Protein Content

Protein quantitation was carried out by two independent methods:

1. UV spectroscopy at 280 nm .

2. Analysis by RP-HPLC, using a calibrated solution of Human I-TAC as a Reference Standard.

Solubility

It is recommended to reconstitute the lyophilized Recombinant Human I-TAC in sterile 18M -cm H2O not less than 100µg/ml, which can then be further diluted to other aqueous solutions.

Stability

Lyophilized I-TAC although stable at room temperature for 3 weeks, should be stored desiccated below -180C. Upon reconstitution I-TAC should be stored at 40C between 2-7 days and for future use below -180C. For long term storage it is recommended to add a carrier protein (0.1% HSA or BSA). Please avoid freeze-thaw cycles.